Adds a dedicated transit-agglobus.md covering the TAD Sud on-demand
service Bénac relies on (booking, schedule, days, destinations), plus
the closest regular line (L3 via Saint-Pierre-de-Rivière), fares, where
to buy tickets, the Zenbus and TixiPASS apps, and SNCF/liO connections.
The transportation.md Public Transit stub now links to it.
